A number of organic compounds exhibiting liquid crystallinity within particular temperature ranges have been disclosed in the art. Furthermore, a number of macromolecules exhibiting liquid crystallinity have been disclosed. These macromolecules contain groups in the main chain or as a dependent group, which exhibit liquid crystallinity. Liquid-crystalline organopolysiloxanes have been disclosed, for example, in Japanese OPI Numbers 56-79173, 57-165480, and 60-252486. Japanese OPI Number 56-79173 describes linear organopolysiloxane having pendant mesogenic groups, similarly, cyclic organopolysiloxanes are described in Japanese OPI Number 57-165480, and branched organopolysiloxanes are described in Japanese OPI Number 60-252486.
However, the methods for the preparation of the liquid-crystalline organopolysiloxanes disclosed in these patent applications consist solely of addition reactions between SiH-containing organopolysiloxanes and alkenyl groups bonded on mesogenic moieties. Noble metal catalysts, e.g., platinum, are used in these addition reactions between alkenyl groups and the silicon-bonded hydrogen atoms in the organopolysiloxanes, i.e. the hydrosilylation reaction, however, these catalysts are easily poisoned. Thus, the reaction is disturbed by the presence of impurities, for example, alkenes, alkynes, amines, phosphorus compounds, sulfur compounds, and organotin compounds, which may be present in the solvents and starting materials, or which may adhere to the walls of the reactor. Furthermore, the synthesis of alkenyl-containing mesogenic compounds is difficult and the yields are also low, making their acquisition both highly problematic and/or very expensive. As a consequence, it is unavoidable that liquid-crystalline organopolysiloxanes synthesized using such compounds will be very expensive.
In order to overcome the above-described problems encountered with the hydrosilylation reaction, the present invention provides a method for the production of liquid-crystalline organopolysiloxanes by which the mesogenic group can be easily introduced into the molecule, while employing readily available materials, and which does not require the use of the hydrosilylation reaction for the introduction of such mesogenic group.